Orthodontic treatment normally involves the application of mechanical forces to urge improperly positioned teeth into correct alignment. One common form of orthodontic treatment includes the use of orthodontic brackets that are fixed to teeth such as by a band around individual teeth or, perhaps more commonly, by adhering the brackets directly to the teeth. A resilient curved archwire is then seated in the archwire slots of the brackets. The archwires are generally attached to the brackets by ligature wires or elastic bands. In some cases, however, self-ligating brackets are used that include a movable cover that selectively closes the labial side of the archwire slot of the brackets. The movable cover is opened for inserting the archwire and then closed for retaining the archwire within the archwire slot. When a patient's teeth are incorrectly leveled and aligned, the archwire elastically deforms to engage the brackets, thereby introducing a force that urges the teeth to move to the correct position over time.
A frequent problem observed during orthodontic treatment is that the archwire tends to move mesially-distally relative to the brackets. The archwire engaged with the bracket slots flexes under forces applied in the oral environment, such as forces applied for chewing and tongue, musculature actions, or orthodontic forces. These unbalanced forces have a tendency to move the archwire through the archwire slots of the brackets in a mesial-distal direction. This movement may cause a free end of the archwire to protrude from one of the brackets attached to the distalmost molars and contact gum or cheek tissue. As a result of the movement, the opposite free end of the archwire may also become disengaged from the bracket that is mounted to the distalmost molar on the opposite side of the mouth cavity. The contact leads to irritation of the gum or cheek tissue. Self-ligating brackets by definition lack structures, such as ligatures and elastic bands, that might limit the mesial-distal movement. Therefore, the mesial-distal movement of the archwire is more pronounced in both active and passive self-ligating brackets.
Several conventional techniques are used to limit the mesial-distal movement of the archwire in the bracket slots. One such technique, for example, is to insert the archwire through a crimpable sleeve, such as a small diameter tube, then position the archwire within the archwire slots with the sleeve located between two adjacent brackets. The sleeve is eventually secured to the archwire at a fixed position by crimping the sleeve to the archwire. The sleeve is configured such that the sleeve cannot pass through or move beyond an archwire slot as the archwire moves in the mesial-distal direction. In this manner, the maximum mesial-distal movement of the archwire is limited to the distance between the adjacent brackets. If the distance between adjacent brackets is sufficiently small, then the free ends of the archwire do not either become disengaged from the bracket or protrude from the bracket for irritating gum or cheek tissue.
A major shortcoming of the conventional technique described above is that the crimpable sleeve is mounted to the archwire in the field, such as a doctor's office, and usually by the dentist or a dental assistant. This field assembly process is often time consuming and may prove frustrating. An archwire has a small cross-sectional profile and a crimpable sleeve has a very small passageway for threading the archwire through the sleeve. Because of the small sizes, the sleeve is difficult to thread onto the archwire. Moreover, during handling of the archwire, such as during its installation into the patient's mouth, the sleeve often slides off one free end of the archwire and onto the floor, or is possibly lost into the patient's mouth. It is often difficult to find a sleeve on the floor after it has fallen off the end of the archwire.
There is thus a need for an improved archwire assembly that eliminates the field assembly and further limits the movement of the sleeve once positioned on the archwire.